1. Field of the Invention
This invention relates to the application of a protective coating to a surface. More particularly, but not exclusively, the invention relates to the applicant of a protective lining to the interior surface of pipes, conduits, tunnels or the like collectively referred to hereafter as pipes, for example water pipes or sewer pipes.
2. Brief Description of the Prior Art
The United Kingdom and other countries have extensive systems of subterranean metal water or sewer pipes which have been laid, in some cases, many year ago. Due to corrosion such systems are becoming more and more prone to leakages and/or blockages due to failure of the pipe walls making an extensive renovation or replacement program desirable. Due to the expense of replacement methods, apparatus and compositions have been developed for applying linings of cement-mortar to the interior of subterranean pipes. By cement-mortar is meant a combination of an inorganic material which sets by reacting with water mixed with it, such as a Portland cement, with an inorganic filling material, such as sand. Depending on their thickness such linings may also provide structural support to the original pipe and provide, in effect, a further pipe within the original pipe. Since many water and sewerage pipes are too small to be entered, or readily entered, by operatives, for example as little as 225 mm, the use of semi- or fully remote-controlled apparatus operable in runs of pipe between existing manholes, which are generally spaced at between about 80 and 150 meters may be necessary or desirable.
In the case of subterranean pipes the application of an internal lining may be by a winched or self-propelled hose-fed pipe-lining machine equipped with means, for example an air motor or otherwise driven centrifugal impeller, to project the coating mixture onto the internal surface of the pipe and a following trailed device such as a trowel, plug or swab device having a surface arranged to be lightly resiliently pressed, in use, towards the surface of the pipe to compact and/or smooth the surface of the lining before it has set. While this system is effective with cement-mortar as such problems may develop when using compositions containing polymeric or resinous additives due to adherence of the composition to smoothing/compacting devices.
West German Patent Publication No. 2627860A relates to a process for lining sections of pipe be by a process in which a mixture of an epoxy resin and an inorganic filler material is introduced into the pipe and is smoothed and compacted by the action of a longitudinally positioned roller having a length corresponding to that of the pipe the roller being in resilient contact with the inner surface of the pipe. In order to prevent the lining composition from sticking to the roller a separating paper sheet is wound around the roller and unwinds as the roller rotates and is allowed to remain on the resinous coating until the latter has cured whereupon the paper is removed. The paper is silicone coated to allow ready release from the cured resin. The procedure of the aforementioned German Patent Publication is not suitable for utilisation on subterranean pipes due to the difficulty of entry thereto of the longitudinal pipe.